how do I get update to 10.14 version?

The Age of the Computer will govern what newer version of macOS it qualifies to Upgrade to. About this Mac will offer the required information. Once the User and determined the age of the computer - following this link to How to get old versions of macOS. You will have to check each version of macOS and see it this computer qualifies for that version OS. Once you decide - Make a Time Machine Backup Now. Only then attempt to download the Full Installer. Be sure to use Only Safari as Other may not work

Notation: Catalina and Above DO NOT support 32 bit application / extension or drivers ( printer, scanner etc. ) Mojave does support 32 bit.

Suggestion: Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and can even corrupt the OS

Does it qualify?

macOS Mojave 10.14.6 - Technical Specifications

General Requirements

OS X 10.8 or later

2GB of memory

12.5GB of available storage (OS X El Capitan 10.11.5 or later)*

Some features require an Apple ID; terms apply.

Some features require a compatible Internet service provider; fees may apply.

Mac Hardware Requirements

For details about your Mac model, click the Apple icon at the top left of your screen and choose About This Mac. These Mac models are compatible with macOS Mojave:

MacBook (Early 2015 or newer)

MacBook Air (Mid 2012 or newer)

MacBook Pro (Mid 2012 or newer)

Mac mini (Late 2012 or newer)

iMac (Late 2012 or newer)

iMac Pro (2017)

Mac Pro (Late 2013; Mid 2010 and Mid 2012 models with recommended Metal-capable graphics cards)

Don't use FireFox for these links…

https://itunes.apple.com/us/app/macos-mojave/id1398502828?mt=12

Go here - Keep your Mac up to date - Apple Support

Can I update my computer to macOS 10.14 version